Double element setback lock

ABSTRACT

A setback lock apparatus is provided for use with an ordinance missile fuze. The lock body has a planar top surface and includes two cavities extending in a generally downward direction into the body of the lock. The first cavity has an opening at its top defined by the intersection of the first cavity with the planar top surface. The second cavity has an opening at its top defined by the intersection of the second cavity and the first cavity. Each cavity contains a steel ball supported by a coil spring. In their initial positions, these steel balls protrude through the openings at the top of their respective cavities. Under the influence of accelerational forces, the steel balls will tend to compress their respective supporting springs and move downward into their respective cavities. However, the masses of the steel balls and the resistances offered by their supporting springs are selected so that the steel ball in the second cavity will initially retard the rearward movement of the steel ball in the first cavity. In addition, after the steel ball in the second cavity permits the rearward movement of the steel ball in the first cavity, it will trap the steel ball at the rear of the first cavity once the accelerational forces decline.

Morrow 1 1 Nov. 25, 1975 DOUBLE ELEMENT SETBACK LOCK [75] Inventor: Warren P. Morrow, Silver Spring,

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, D.C.

[22] Filed: May 10, 1974 [21] Appl. No.: 468,718

[52] U.S. Cl 102/78; 102/73 [51] Int. Cl. F42C 15/29 [58] Field of Search 102/78, 80, 75, 76, 79, 102/81, 73

[56] References Cited UNITED STATES PATENTS 1,744,194 1/1930 Adelman 102/80 2,625,881 l/1953 Rabinow 102/78 2,712,284 7/1955 Thomas et a1.. 102/80 X 2,733,659 2/1956 Booth 102/79 3,136,252 6/1964 De Sabla et a1. 102/78 FOREIGN PATENTS OR APPLICATIONS 1,113,885 9/1961 Germany 102/79 1,143,740 2/1963 Germany 102/78 1,250,350 11/1960 France 102/78 Primary ExaminerSamuel Feinberg Assistant ExaminerHarold Tudor Attorney, Agent, or Firm-Nathan Edelberg; Robert P. Gibson; Saul Elbaum [57] ABSTRACT A setback lock apparatus is provided for use with an ordinance missile fuze. The lock body has a planar top surface and includes two cavities extending in a generally downward direction into the body of the lock. The first cavity has an opening at its top defined by the intersection of the first cavity with the planar top surface. The second cavity has an opening at its top defined by the intersection of the second cavity and the first cavity. Each cavity contains a steel ball supported by a coil spring. In their initial positions, these steel balls protrude through the openings at the top of their respective cavities. Under the influence of accelerational forces, the steel balls will tend to compress their respective supporting springs and move downward into their respective cavities. However, the masses of the steel balls and the resistances offered by their supporting springs are selected so that the steel ball in the second cavity will initially retard the rearward movement of the steel ball in the first cavity. In addition, after the steel ball in the second cavity permits the rearward movement of the steel ball in the first cavity, it will trap the steel ball at the rear of the first cavity once the accelerational forces decline.

10 Claims, 8 Drawing Figures Sheet 1 of2 r my i 2051568- US. Patent Nov. 25, 1975 TIME U.S. Patent Nov. 25, 1975 Sheet20f2 3,921,531

DOUBLE ELEMENT SETBACK LOCK RIGHTS OF THE GOVERNMENT The invention described herein may be manufactured, used, and licensed by or for the United States Government for governmental purposes without the payment to me of any royalties thereof.

BACKGROUND OF THE INVENTION .The present invention relates generally to a safety setback lock or release for ordnance devices and more particularly to a device for arming the fuze of an ordnance missile only after a predetermined period of sustained acceleration such as occurs, for example, in the discharge of a rocket.

In ordnance missiles, which commonly carry explosive charges, it is desirable that the missiles remain safe or unarmed until they have been fired. This unarmed state insures maximum safety of the personnel using the missile and enables the explosive to cause damage to the target. Various means have been used to secure this result. For example, rotating missiles have been equipped with arming mechanisms which are responsive to the centrifugal forces developed when the missile is fired. Non-rotating missiles, such as mortar shells, certain classes of rockets and the like, have been equipped with arming mechanisms which are responsive to the forces of setback, which occurs when the missile is launched. However, in US. Pat. No. 2,625,881, there is shown such an arming mechanism which includes a particular double element release which is responsive to sustained acceleration only. The double element release mechanism includes a pair of spring mass systems wherein the masses are a pair of concentric sliding cylinders.

SUMMARY OF THE INVENTION The present invention provides a setback lock apparatus for use with an ordnance missile fuze. The lock apparatus has a body with a planar top surface and a first cavity extending in a generally downward direction into the locked body. The first cavity has an opening at its top defined by the intersection of the first cavity with the planar top surface. A second cavity is contained entirely within the locked body. A first spring is situated within the first cavity and a first mass also is situated in the first cavity in contact with the first spring. The first mass is operative in a rest position to protrude through the opening at the top of the first cavity and is operative under accelerational forces to move downward into the first cavity and compress the first spring. A second spring is situated within the second cavity and a second mass, also situated in the second cavity, is in contact with the second spring. The second mass is operative under low accelerational forces to block the movement of the first mass within the first cavity and is operative under high accelerational forces to move downward into the second cavity and compress the second spring, thus permitting the downward movement of the first mass.

OBJECTS OF THE INVENTION An object of the present invention is the provision of an improved setback lock apparatus.

Another object of the present invention is the provision of a setback lock apparatus which is simple in construction and therefore easy to manufacture.

A further object of the present invention is the provision of a setback lock apparatus which is both reliable and inexpensive to manufacture.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal section of a projectile detonator for a fuze nose embodying the present invention.

FIG. 2 is a longitudinal section to a greatly enlarged scale of the preferred embodiment of the set back safety lock shown in FIG. 1 in its initial or safe condition.

FIG. 3 is a graph of acceleration versus time to illustrate the action of the setback lock of the present invention;

FIGS. 4, 5, 6 and 7 are schematic representations of the action of the setback safety lock of the present invention; and

FIG. 8 is a schematic representation of a second embodiment of the setback lock of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an example is shown of the environment in which the'safety setback lock apparatus of the present invention may be used. A fuze 10 is adapted to be screwed into the nose of a projectile (not shown) by means of threads 12. The fuze 10 contains a transverse bore 14 which is closed by a threaded block 16. The transverse bore 14 contains a slidable plastic element 18, which may be suitably keyed to prevent rotation in the bore 14. The slidable plastic element 18 is shown as being biased to the right by spring 20, and is restrained against displacement by the safety setback lock of the present invention generally indicated at 30. Part of the safety setback lock 30 projects into a recess 32 in bore 14 to thereby prevent the movement of slidable plastic elements 18. It is apparent that if the projection on the setback lock 30 is withdrawn into the lock mechanism, the slidable plastic element 18 will move to the right until a detonator 34 is aligned with a firing pin 36 to thereby arm the fuze 10 in a known fashion. Upon impact, the detonator 34 will be fired by the pin 36 which will in turn set off a booster 38 to explode the projectile charge. It should be understood, of course, that in place of the impact mechanism shown, any other type of fuze mechanism may be employed. The present invention is concerned primarily with the setback lock apparatus 30 which will now be described in more detail with reference to FIGS. 27.

FIG. 2 is a greatly enlarged longitudinal section of the setback lock apparatus of the present invention shown in its initial or safe condition. The setback lock apparatus includes a body portion 40 having upper and lower sections 42 and 44 respectively, which are securely joined, preferably by bolts 46. The lock body 40 is preferably in the shape of a right circular cylinder; however, any shape that will permit the lock body to be retained within and slide with the plastic element 18 would be suitable. The lock body may be constructed of numerous materials but is preferably constructed of a cast metal. The top portion 42 of the lock body includes a planar top surface 48. Extending in a generally downward direction from the planar top surface into the lock body is a first cavity 50. This first cavity houses first mass spring system comprising a first coiled spring 52 and a first mass 54. The coil spring 52 is seated at the bottom of the cavity 50 and is designed so that its top portion 56 is always in contact with the mass 54. The mass 54 is preferably a steel ball which is retained within the cavity 50 by a lip portion 58 at the top of the cavity 50. The opening at the top of the cavity 50 is defined by the intersection of the cavity walls 60 and the planar top surface 48. The cavity 50 is preferably in the shape of a right circular cylinder, the wall 60 of which is inclined with respect to the planar top surface 48 at an angle a which is preferably 45.

The lock body 40 also contains a second cavity 62 which opens into the side wall 60 of the first cavity 50 and extends in a generally downward direction therefrom. The cavity 62 houses a second mass spring system composed of coil spring 64 and mass 66. The mass 66 is preferably a steel ball of slightly larger diameter than the steel ball 54. The spring 66 is seated at the bottom of the cavity 62 and its top portion 68 is always in contact with the steel ball 66. The cavity 62 is preferably cylindrical in shape and its side walls 70 form an angle B with the walls 60 of the first cavity 50. The angle [3 is preferably 90. The steel ball 66 is retained within cavity 62 by a lip portion 72 at the top opening of cavity 62.

FIG. 3 shows a graph of acceleration versus time for the projectile in which the setback lock 30 is to be housed. FIG. 2 shows the setback lock apparatus at time t At this point in time, the setback lock is subject to no accelerational forces other than the force of gravity and the force applied to the steel ball 54 by the spring 52 is sufficient to cause it to protrude through the opening at the top of the cavity 50 and thus block any lateral movement by the setback lock 30 within the bore 14.

FIGS. 4-7 show schematically the operation of the setback lock 30 during the flight of the projectile in which it is housed. FIG. 4 depicts the lock at time 1. At this point in time, because of the design of the first spring mass system and because of the accelerational forces applied to the lock, the steel ball 54 begins to overcome the force applied to it by the spring 52 and starts to travel toward the base of the cavity 50. However, the second spring mass system is designed so that at this point in time, the second steel ball 66 has not yet started to overcome the force applied to it by the spring 64. Since the steel ball 66 protrudes into the cavity 50, the downward travel of the steel ball 54 is blocked, and therefore, the lock 30 retains its position within the bore 14.

FIG. 5 shows the action of the lock at time 1 At this point in time, accelerational forces have built up to the point where the force applied to the steel ball 66 by the spring 64 is no longer sufficient to retard the downward movement of the steel ball 66. Therefore, the ball 66 starts to move downward, compressing the spring 64. Since the downward path of steel ball 53 is no longer blocked, the steel ball 54 is now free to move downward, compressing spring 52. Now that the steel ball 54 no longer protrudes beyond planar surface 48, the lateral movement of the lock 30 within bore 14 is no longer retarded.

FIG. 6 shows the relative position of the steel balls 54 and 66 at time 1 At this point in time, the acceleration of the projectile in which the lock 30 is travelling is starting to decrease and the accelerational forces applied to the ball 66 are no longer sufficient to overcome the force applied to the ball 66 by the spring 64. Therefore, the ball 66 moves in an upward direction within the cavity 62, once again protruding into the cavity 50.

FIG. 7 depicts the action of the lock 30 at time I.,. At this point in time, the acceleration of the projectile in which the lock is travelling has decreased to the point where the accelerational forces to which the ball 54 is subjected are no longer sufficient to overcome the force applied to the ball 54 by the spring 52. Therefore, the ball 54 starts to move in an upward direction within the cavity 50. However, since the upward path of the ball is now blocked by the steel ball 66, the steel ball 54 is trapped within the bottom of the cavity 50. Thus, the plastic slidable element 18 will be pushed laterally by the spring 20 within the bore 14 until detonator 34 is aligned with firing pin 36.

With reference to FIG. 8, a second embodiment of the setback lock apparatus of the present invention will be described in schematic form only, with elements like those described in the embodiment shown in FIG. 2 being identified by like numerals.

The first and second cavities 50 and 62, respectively, are parallel to each other, with their walls 60 and 70, respectively, being perpendicular to the planar top surface 48. The first cavity 50 houses a spring 52 and a steel ball 54 as before. Likewise, the second cavity 62 houses a spring 64 and a steel ball 66. A third cavity 74 is provided having an axis parallel to the planar top surface 48 and perpendicular to the walls 60 and of first and second cavities 50 and 62, respectively. The third cavity 74 has openings at both ends defined by the intersection of the third cavity with the walls of the first cavity 60 and the second cavity 70. I-Ioused within the third cavity is a rod 76 having a shoulder portion 78 and a spring 80 which abuts the shoulder portion 78 and biases the rod 76 toward the second cavity 62. The rod 76 is slightly longer than the cavity 74 so that at any point in time it must extend beyond at least one end of the cavity 74.

The action of this second embodiment of the setback lock of the present invention is quite similar to the action of the first embodiment. Thus, at time t the steel ball 54 protrudes beyond the planar top surface 48 and prevents any lateral movement of the lock. At time t accelerational forces on the steel ball 54 are such that it starts to override the force of the spring 50; however, any downward movement is blocked by the rod 76. At time t the accelerational force on the steel ball 66 begins to override the counteracting force of the spring 64 and the steel ball 66 begins to move downward within the cavity 62. The downward movement of the steel ball 66 permits lateral movement of the spring biased rod 76 into the cavity 62. Thus, the rod 76 no longer protrudes into the first cacity 50 and the steel ball 54 is free to move in a downward direction, compressing spring 52. At time accelerational forces on the steel ball 66 start to decrease to the point where the force applied by the spring 64 pushes the steel ball 66 in an upward direction within the cavity 62, forcing the rod 76 to move laterally into the cavity 50. At time t,, accelerational forces on the steel ball 54 have decreased to the point where the force applied by the spring 52 is sufficient to move the ball 54 in an upward direction within cavity 50. However, this upward movement is now blocked by the rod 76 and the ball 54 is trapped in the bottom of the cavity 50. Thus, the setback lock 30 is free to move laterallly within the bore Thus, it is apparent that the setback lock apparatus of the present invention is quite efficient in operation while at the same time, being very simple and inexpensive in construction. Steel balls and coil springs are exceptionally low in cost and are available in standard sizes, thus allowing a great deal of flexibility in the design of a particular system. Furthermore, if desired, other ball spring combinations (for example, a third cavity with a third ball spring system set to move at an even higher accelerational level) may be used to yield even greater safety.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications can be made by a person skilled in the art.

What is claimed is:

l. A setback lock apparatus for use with an ordnance missile fuze comprising:

a. a body having:

1. a planar top surface,

2. a first cavity extending in a generally downward direction into said body, said first cavity having an opening at its top defined by the intersection of said first cavity with said planar top surface, and

3. a second cavity contained entirely within said body, said second cavity intersects said first cavity and has an opening at its top defined by the intersection of the top of said second cavity and the side of said first cavity below said planar top surface;

b. a first spring situated within said first cavity;

c. a first mass situated in said first cavity and in contact with said first spring, said first mass being operative in a rest position to protrude through the opening at the top of said first cavity and operative under accelerational forces to move downward into said first cavity and compress said first spring;

d. a second .spring situated within said second cavity;

and

e. a second mass situated in said second cavity and in contact with said second spring, said second mass being operative in a rest position and under low acceleration forces to protrude through the opening at the top of said second cavity to block the movement of said first mass within said first cavity and being operative under high accelerational forces to move downward into said second cavity, compress said second spring and permit the downward movement of said first mass.

2. A setback lock apparatus as set forth in claim 1 wherein said first mass and said second mass are spherical, said second mass being slightly larger in diameter than said first mass.

3. A setback lock apparatus as set forth in claim 2 wherein said first mass and said second mass are steel balls.

4. A setback lock apparatus as set forth in claim 1 wherein each of the openings at the tops of said first and second cavities includes a lip portion for retaining said first and second masses within said cavities.

5. A setback lock apparatus as set forth in claim 1 wherein said first cavity and said second cavity are generally cylindrical and the sides of said first cylindrical cavity and the sides of said second cylindrical cavity form acute angles with respect to said planar top surface.

6. A setback lock apparatus for use with an ordnance missile fuze comprising:

a. a body having:

1. a planar top surface,

2. a first cavity extending in a downward direction into said body perpendicular to said planar top surface, said first cavity having an opening at its top defined by the intersection of said first cavity with said planar top surface,

3. a second cavity contained entirely within said body having its major axis perpendicular to said planar top surface, and

4. a third cavity contained entirely within said body located below and havings its major axis parallel to said top planar surface, said third cavity intersecting each of said first and second cavities, and having openings at both ends defined by the intersections of said third cavity with said first and second cavities;

b. a first spring situated within said first cavity;

0. a first mass situated in said first cavity and in contact with said first spring, said first mass being operative in a rest position to protrude through the opening at the top of said first cavity and operative under accelerational forces to move downward into said first cavity and compress said first spring;

(1. a second spring situated within said second cavity;

e. a second mass situated in said second cavity and in contact with said second spring, said second mass being operative in a rest position and under low accelerational forces to block the intersection of said second and said third cavities and being operative under high accelerational forces to move downward into said second cavity, compress said second spring and unblocking the intersection of said second and said third cavities;

f. a third spring situated within said third cavity; and

g. a third mass situated in said third cavity and in contact with said third spring, said third mass being operative in a rest position in cooperation with said second mass to protrude through the opening at the intersection of said first and third cavities, and operative under accelerational forces to be released by said second mass and protrude through the opening at the intersection of said second and third cavities.

7. A setback lock apparatus as set forth in claim 6 wherein said first mass and said second mass are spherical, said second mass being slightly larger in diameter than said first mass.

8. A setback lock apparatus as set forth in claim 7 wherein said first, second and third cavities are generally cylindrical.

9. A setback lock apparatus as set forth in claim 6 wherein said third mass is a rod having a length greater than the length of said third cavity, a collar mounted to said rod, said third spring is in contact with said collar and one end of said third cavity for biasing said rod towards said second cavity.

10. A setback lock apparatus as set forth in claim 7 wherein the opening at the top of said first cavity includes a lip portion for retaining said first mass within 

1. A setback lock apparatus for use with an ordnance missile fuze comprising: a. a body having:
 1. a planar top surface,
 2. a first cavity extending in a generally downward direction into said body, said first cavity having an opening at its top defined by the intersection of said first cavity with said planar top surface, and
 3. a second cavity contained entirely within said body, said second cavity intersects said first cavity and has an opening at its top defined by the intersection of the top of said second cavity and the side of said first cavity below said planar top surface; b. a first spring situated within said first cavity; c. a first mass situated in said first cavity and in contact with said first spring, said first mass being operative in a rest position to protrude through the opening at the top of said first cavity and operative under accelerational forces to move downward into said first cavity and compress said first spring; d. a second spring situated within said second cavity; and e. a second mass situated in said second cavity and in contact with said second spring, said second mass being operative in a rest position and under low acceleration forces to protrude through the opening at the top of said second cavity to block the movement of said first mass within said first cavity and being operative under high accelerational forces to move downward into said second cavity, compress said second spring and permit the downward movement of said first mass.
 2. a first cavity extending in a generally downward direction into said body, said first cavity having an opening at its top defined by the intersection of said first cavity with said planar top surface, and
 2. A setback lock apparatus as set forth in claim 1 wherein said first mass and said second mass are spherical, said second mass being slightly larger in diameter than said first mass.
 2. a first cavity extending in a downward direction into said body perpendicular to said planar top surface, said first cavity having an opening at its top defined by the intersection of said first cavity with said planar top surface,
 3. a second cavity contained entirely within said body having its major axis perpendicular to said planar top surface, and
 3. a second cavity contained entirely within said body, said second cavity intersects said first cavity and has an opening at its top defined by the intersection of the top of said second cavity and the side of said first cavity below said planar top surface; b. a first spring situated within said first cavity; c. a first mass situated in said first cavity and in contact with said first spring, said first mass being operative in a rest position to protrude through the opening at the top of said first cavity and operative under accelerational forces to move downward into said first cavity and compress said first spring; d. a second spring situated within said second cavity; and e. a second mass situated in said second cavity and in contact with said second spring, said second mass being operative in a rest position and under low acceleration forces to protrude through the opening at the top of said second cavity to block the movement of said first mass within said first cavity and being operative under high accelerational forces to move downward into said second cavity, compress said second spring and permit the downward movement of said first mass.
 3. A setback lock apparatus as set forth in claim 2 wherein said first mass and said second mass are steel balls.
 4. A setback lock apparatus as set forth in claim 1 wherein each of the openings at the tops of said first and second cavities includes a lip portion for retaining said first and second masses within said cavities.
 4. a third cavity contained entirely within said body located below and havings its major axis parallel to said top planar surface, said third cavity intersecting each of said first and second cavities, and having openings at both ends defined by the intersections of said third cavity with said first and second cavities; b. a first spring situated within said first cavity; c. a first mass situated in said first cavity and in contacT with said first spring, said first mass being operative in a rest position to protrude through the opening at the top of said first cavity and operative under accelerational forces to move downward into said first cavity and compress said first spring; d. a second spring situated within said second cavity; e. a second mass situated in said second cavity and in contact with said second spring, said second mass being operative in a rest position and under low accelerational forces to block the intersection of said second and said third cavities and being operative under high accelerational forces to move downward into said second cavity, compress said second spring and unblocking the intersection of said second and said third cavities; f. a third spring situated within said third cavity; and g. a third mass situated in said third cavity and in contact with said third spring, said third mass being operative in a rest position in cooperation with said second mass to protrude through the opening at the intersection of said first and third cavities, and operative under accelerational forces to be released by said second mass and protrude through the opening at the intersection of said second and third cavities.
 5. A setback lock apparatus as set forth in claim 1 wherein said first cavity and said second cavity are generally cylindrical and the sides of said first cylindrical cavity and the sides of said second cylindrical cavity form acute angles with respect to said planar top surface.
 6. A setback lock apparatus for use with an ordnance missile fuze comprising: a. a body having:
 1. a planar top surface,
 2. a first cavity extending in a downward direction into said body perpendicular to said planar top surface, said first cavity having an opening at its top defined by the intersection of said first cavity with said planar top surface,
 3. a second cavity contained entirely within said body having its major axis perpendicular to said planar top surface, and
 4. a third cavity contained entirely within said body located below and havings its major axis parallel to said top planar surface, said third cavity intersecting each of said first and second cavities, and having openings at both ends defined by the intersections of said third cavity with said first and second cavities; b. a first spring situated within said first cavity; c. a first mass situated in said first cavity and in contacT with said first spring, said first mass being operative in a rest position to protrude through the opening at the top of said first cavity and operative under accelerational forces to move downward into said first cavity and compress said first spring; d. a second spring situated within said second cavity; e. a second mass situated in said second cavity and in contact with said second spring, said second mass being operative in a rest position and under low accelerational forces to block the intersection of said second and said third cavities and being operative under high accelerational forces to move downward into said second cavity, compress said second spring and unblocking the intersection of said second and said third cavities; f. a third spring situated within said third cavity; and g. a third mass situated in said third cavity and in contact with said third spring, said third mass being operative in a rest position in cooperation with said second mass to protrude through the opening at the intersection of said first and third cavities, and operative under accelerational forces to be released by said second mass and protrude through the opening at the intersection of said second and third cavities.
 7. A setback lock apparatus as set forth in claim 6 wherein said first mass and said second mass are spherical, said second mass being slightly larger in diameter than said first mass.
 8. A setback lock apparatus as set forth in claim 7 wherein said first, second and third cavities are generally cylindrical.
 9. A setback lock apparatus as set forth in claim 6 wherein said third mass is a rod having a length greater than the length of said third cavity, a collar mounted to said rod, said third spring is in contact with said collar and one end of said third cavity for biasing said rod towards said second cavity.
 10. A setback lock apparatus as set forth in claim 7 wherein the opening at the top of said first cavity includes a lip portion for retaining said first mass within said cavity. 